1. Field of the Invention
The present invention relates to manufacturing, field service, maintenance and performance aspects of optical readers and components thereof. More particularly, the present invention relates to quality factors that may be generated for such purposes.
2. Background Information
Optical readers are found in many systems, including scanners, copy machines, and document readers, such as, e.g., reader systems for processing markings in an image of a form, such as a lottery playslip. Lottery playslips include, e.g., cards, tickets, and other printed media that may identify a player's selection(s) in a lottery transaction. More particularly, playslips are used by a player to purchase a lottery ticket bearing a player's number selections. The markings on lottery playslips are processed to determine and verify the numbers selected by a player for an upcoming lottery drawing.
Optical reader systems typically include a motor assembly, an illumination source, a sensor array, and a computer processing system. The illumination source and sensor array may be part of a bar assembly that is positioned across the readable width of a document. The document and the bar assembly may move relative to each other to accomplish the scanning of the entire length of the document. In operation, the motor assembly may provide the relative motion so that each row across the width of the document may be scanned for the length of the entire document.
The illumination source may include a series of light emitting diodes (LEDs) and the sensor array may include a set of photo-transistors. Both the illumination source and the sensor array may be distributed along the bar assembly across the readable width of the document. The light from the LEDs is reflected from the document onto the sensors. Other illumination sources, e.g., flash tubes, fixed halogens, etc., may be used; and, other photo-sensors, e.g., photo-diodes, photo-resistors, etc., also may be used. In short, the present invention may find advantageous use with virtually any optical reader with any light source and with any sensor.
In this environment, each photo-sensor represents a pixel and the intensity of the reflected light corresponds to the scene on the document. When the document is illuminated, more light is reflected from light areas and less from dark areas; and the output level of a photo-sensor corresponds to the intensity of the light that is received by that pixel. The photo-sensors (pixels) are electronically scanned across the width of the document for each successive row along the length of the entire document. Illustratively, the height of each row may be determined by the motor assembly design, and the height may be equal to the width of a pixel.
Herein, the words and phrases “scanned,” “read out”, “sampled”, and “clocked out” may be used interchangeably.
In the above description, the document may be driven across a stationary illumination bar, or the illumination bar may be driven across the document as the document remains in a stationary position such as, e.g., a document disposed on a platen.
In a calibrated reader, the relative outputs of the pixels over a gray scale dynamic range are balanced and output consistent values. That is, the outputs of all the pixels are substantially the same for the same scene, from the black area to the white area. In order to calibrate an optical reader, the light source, the photo-sensors and a gray scale target must be optimized to read the full black to white gray scale dynamic range. And, to be commercially competitive, it is important to measure and confirm the performance of a reader in the field.
Presently, components and sub-assemblies for optical readers are sample tested before they are incorporated into the optical reader and the reader is shipped to a customer. The reader itself is tested and calibrated by a quality assurance group that certifies its performance before shipping. Typically, once a reader is placed in the field, the manufacturer is only informed of a problem when a warranty issue or a service complaint is received. The reader may lose calibration due to, inter alia, a change in the characteristics of the light sources and/or the photo-sensitive devices. Typically, the response to a warranty issue or service complaint is a visit from a field service technician. And, between the time that the issue first arises or the complaint is made, and the time that the service to a reader is afforded, the reader is down. As a result, these service practices are slow, costly and customer unfriendly.
In view of the foregoing, it would be advantageous to generate a quality factor that indicates the performance of an optical reader during manufacturing and that can be tracked over time for optical readers in the field. It would be, moreover, advantageous if the quality factor was measurable on-line, while a reader is in service.